The main focus of the Auditory Research Lab is using otoacoustic emissions (OAEs) as a non-invasive probe of human auditory function. OAEs are very soft sounds that arise as a by-product of normal cochlear function and can be recorded using tiny loudspeakers and microphones placed in the ear canal. Changes in cochlear function result in changes in OAE amplitude and phase. These changes provide non-invasive, indirect measures of cochlear status.
One of the main areas of focus for the Auditory Research Lab is measuring OAEs at extended high frequencies. Standard clinical measurement of OAEs focuses on frequencies from 0.5 to 5 kHz. By modifying existing equipment, it is possible to measure OAEs at frequencies up to 20 kHz. Measuring OAEs at these extended high frequencies may provide information useful for early detection of hearing loss due to noise exposure or ototoxicity.
The ARL is equipped for acoustic measurements and analysis. The laboratory space includes a 9' X 8' double-walled sound booth. The lab also has access to the department's anechoic chamber. Measurement equipment includes a Larson Davis 824 sound level meter, G.R.A.S. IEC 711 ear simulator, KEMAR acoustics research mannequin, and Etymotic Research ER-10B+ and ER-10C otoacoustic emissions probes. Data acquisition is typically made using 24-bit Lynx sound cards, PC with Windows XP, and custom software written in MATLAB. Various TDT System 3 components are also used, including HB7 headphone buffers, MA3 microphone amplifier, SM5 signal mixer, and PA5 programmable attenuators that can be controlled from MATLAB using ActiveX. Signal processing and data analysis are done with MATLAB. For audiometric testing, the ARL has a Madsen Equinox diagnostic audiometer and a GN Otometrics Otoflex 100 impedance bridge.
Auditory Research Laboratory
Dr. Shawn S. Goodman, Director
341 Wendell Johnson Speech and Hearing Center
The University of Iowa
Iowa City IA 52242